JAJSU42A April 2022 – April 2024 BQ76922
PRODUCTION DATA
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The HDQ interface is an asynchronous return-to-one protocol where a processor communicates with the BQ76922 device using a single-wire connection to the ALERT pin. Both the controller (host device) and responder (BQ76922) drive the HDQ interface using an open-drain driver, with a pullup resistor from the HDQ interface to a supply voltage required on the circuit board. The BQ76922 device can be changed from the default communication mode to HDQ communication mode by setting the Settings:Configuration:Comm Type configuration register, or sending a subcommand (at which point the device switches to HDQ mode immediately). Note that the SWAP_COMM_MODE() subcommand immediately changes the communications interface to that selected by the Comm Type configuration, while the SWAP_TO_HDQ() subcommand immediately changes the interface to HDQ using the ALERT pin.
With HDQ, the least significant bit (LSB) of a data byte (command) or word (data) is transmitted first.
The 8-bit command code consists of two fields: the 7-bit HDQ command code (bits 0–6) and the 1-bit R/W field (MSB Bit 7). The R/W field directs the device to do one of the following:
The HDQ peripheral on the BQ76922 device can transmit and receive data as an HDQ responder only.
The return-to-one data bit frame of HDQ consists of the following sections: